Preparation of 4-pregnen-17alpha-ol-3, 20-dione



2,777,843 PREPARATION or 4-PREGNEN-17a-OL-3,20-DIONE No Drawing.Application December Serial No. 472,756

Claims. (Cl. 260-23955) This invention relates to the preparation of4-pregnen- 17a-ol-3,20-dione and particularly to the preparation of4-pregnen-17a-ol-3,20-dione from S-haIo-bisnorcholanal, and tointermediates thus obtained.

The discovery of the remarkable properties of cortisone andhydrocortisone and similar related compounds, has stimulated Wideinterest in finding simpler and more economical methods of preparingsuch compounds. One of the more recent methods which has been developedfor preparing these valuable steroids is the introduction of oxygengroups by subjecting desoxy steroids to the action of microorganisms.This development has led to the increasing importance of desoxy steroidswhich possess all the necessary groups with the exception of oxygengroups which may be introduced by fermentation methods. One of the morevaluable of these desoxy steroids is 4-pregnen-17a-ol-3,20-dione whichonly lacks the 11-keto and 21-hydroxy groups of cortisone, and the 1118and 21-hydroxy groups of hydrocortisone. These oxygen groups can beadded by fermenting the steroid with various microorganisms, as forexample, fermentation with various strains of Curvularia will introducean llp-hydroxy group, and fermentation with various strains ofSphaeroidaceae will introduce a 21-hydroxy group.

The preparation of 4-pregnen-17a-o1-3,20-dione has heretofore beencarried out by a costly and complex process which involved theenolization of bisnorcholanal followed by ozonization of the resultingenol ester, reductive decomposition of the ozonide to the correspondingZI-keto-pregnane, enolization of this compound to form a A-2O-acetoxy-pregnane, peracid oxidation of the 17,20 double bond toproduce the 17,20 cpoxide derivative of the unsaturated ester, andfinally hydrolysis of this compound to produce4-pregnen-17a-ol-3,20-dione.

It has been suggested to prepare Sa-halo-bisnorcholanic acids andaldehydes starting with stigmasterol. The halogen in theSa-halo-bisnorcholanic aldehydes represents a potential double bond andyet is impervious to attack during the oxidation of the 3-hydroxyl groupto the 3-keto group.

An object of the invention is to provide a simplified procedure forproducing 4-pregnen-17a-ol-3,20-dione from readily available startingmaterial. Another object of the invention is to provide a process forthe degradation of the aldehyde group in Set-halo-bisnorcholanaldehydeto the l7a-hydroxy-20-keto side-chain without removal of the Sit-halogroup. A further object is to provide valuable intermediates useful inthis process. Other objects and the advantages of the invention willappear hereinafter.

In accordance with the invention, 4-pregnen-17d-ol- 3,20-dione (CompoundVII) is prepared .by the following series of reactions: brominating aS-halo-bisnorcholanal compound (Compound I) to produce the corresponding5 -halo- 20-bromo-bisnorcholanal compound (Compound II),dehydrobrominating to producetthe correspondingS-halo-l7(20)-bisnorcholenal compound (Compound III), treating withperacid to produce the nited States Patent I 2,777,843 Patented Jam'lS,1957 2 corresponding epoxy formate (Compound IV), hydrolyzing to yield 5halo-pregnane-3,17a-diol-20-one (Compound V), oxidation of the 3-hydroxygroup to form a keto group (Compound VI) and dehydrohalogenating toproduce 4-pregnen-17a-ol-3,20-dione (Compound VII).

As alternate steps to this procedure, the S-halo-bisnorcholanal compound(Compound I). is converted directly to the correspondingS-halo-l7-(20)-bisnorcholenal (Compound III) by reacting with bromine inthe presence of a weak base and a catalyst. The epoxy formate (CompoundIV). is. converted to 5 -pregnene-3,17a-diol- 20-one by saponification.7

These reactions may be chemically represented wherein R is a groupconvertible to a hydroxy group by hydrolysis and X is a halogen asfollows:

r r O0-OHO' Br-O-OHO Compound I Compound II t l R I? CO-OH (IJH CompoundIV Compound III O: I :---,on

Compound VI Compound VII The S-halo-bisnorcholaual compound isbrominated produce the corresponding -halo-20-bromo-bisnorcholanai. TheS-halo-bisnorcholanal compound has either a Soc-ChlOIO or Sa-bromo groupand a substituent at the 3-position which may be readily hydrolyzed to ahydroxy group, such as an ether group of the formula 08?, wherein R is ahydrocarbon group and especially a hydrocarbon radical containing up toand including eight carbon atoms, e. g. methyl, ethyl, propyl,isopropyl, butyl, hexyl, cyclohexyl, benzyl and the like, or an estergroup of the formula OCOR wherein R is ahydrocarbon radical, especiallyhydrocarbon radicals containing up to and including seven carbon atoms,such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, heptyl, phenyl,cyclohexyl, and the like.

The bromination may be conveniently carried out by dissolving orsuspending the S-halo-bisnorcholanal in an organic solvent andsubjecting the solution or suspension to the action of approximately anequal molar amount of bromine. There is sufficient hydrogen bromideformed during the reaction to act as a catalyst. It is preferred to usechloroform as a solvent, although other solvents may be used, such asacetic acid, formamide and mixtures of solvents, such as aceticacid-pyridine and acetic acidformamide. The reaction temperature governsthe rate of bromination, thus the rate of bromination increases atelevated temperatures. It is ordinarily desired, for convenience, toeffect the bromination at about 20 to 60 C. although temperatures as lowas 0 C. can be used under normal atmospheric pressure. Within thepreferred temperature range the reaction usually is complete in fromone-half to six hours.

The S-halo-ZO-brorno-bisnorcholanal compound is readilydehydrobrominated to produce the corresponding S-halo-17 (20)-bisnorcholenal. The. dehydrobromination can be readily carried out byheating with metallic halides particularly with lithium chloride in anamide solvent, such as a N,N-dialkylacylamides having the formulawherein R, R" and R' are alkyl groups containing from one to six carbonatoms, as for example, N,N-dimethylformamide, N.N-dimethylacetamide,N,N-diethylformamide, N,N-diethylacetamide, N-methyl-N-ethylformamide,N,N-dimethylpropirnamide and N-rnethyl-N-ethylacetamide. Other metallichalides which may be used are magnesium chloride, beryllium chloride,and aluminum chloride. Hydrogen bromide has also been found to beetfective in place of the metallic halide. The dehydrobromination mayalso be carried out by the use of col lidine, pyridine, lutidine,diethylaniline, or other organic bases which are refluxed with thebromo-steroid for a period of time of the order of 15 minutes. Theproduct can be recovered by filtering, washing with water, and drying.

The S-halo-bisnorcholanal compound is converted directly to thecorresponding S-halo-l7(20)-bisnorcholenal compound. This may be readilycarried out by reacting the bisnorcholanal with bromine in the presenceof a weak base. The weak base is preferably a N,N-dialkylacylamidehaving the formula It 0 ll /I\1-CR'" RI! wherein R, R" and R' are asdefined above. Typical examples of such amides are:N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropamide,N,N- diethylforrnamide, N,N-diethylacetamide, N-methyl-N-ethylformamide, and N-methyl-N-ethylacetamide. The reaction time isreduced by the addition of any of the ordinarily use brominationcatalysts such as hydrogen bromide, sulfuric acid or organic sulfonicacids as for produce S-halo-pregnan- 17 a-ol-3,20-dione.

example p-toluene sulfonic acid. The reaction is conveniently carriedout at room temperature which requires from 12 to 28 hours forcompletion. The product can be recovered by diluting the reactionmixture with water, filtering, and then washing the product with waterand drying.

The 5-halo-l7(20)-bisnorcholenal compound is treated with an organicperacid to produce the corresponding epoxy formate(Se-halo-17,20-epoxy-pregnan-20-ol-3-R 20-formate). The organic peracidis preferably an aromatic percarboxylic acid, such as perbenzoic andperphthalic acids, and saturated aliphatic peracids, such as per-aceticand persuccinic acids. This reaction results in nearly quantatitiveyield of product. The reaction is preferably carried out in an organicsolvent, such as benzene, chloroform, or ethyl acetate. The reaction ispreferably carried at from minus 10 to 50 C., although the temperaturemay be varied Within wide limits. At the preferred temperature range thereaction requires from 12. to 48 hours for completion. The rate ofreaction will vary with the temperature. The product can be isolatedfrom the reaction mixture by filtering to remove various insolublebyproducts and reactants, and then washing with water containing sodiumcarbonate. The organic layer is dried over sodium carbonate andevaporated to dryness under vacuum. The product can also be recovered byether extraction followed by washing with dilute alkali and water, andevaporating to dryness.

The 5a-halo-l7,20-epoxy-pregnan-20-ol-3-R 20 formate is hydrolyzed toyield 5-halo-pregnane-3,17a-diol-2G-one. The hydrolysis is readilyachieved by treating with an acid in a suitable solvent, such asmethanol, ethanol, acetone, or tetrahydrofuran. Strong acid such ashydrochloric acid, sulfuric acid, perchloric acid, andparatoluene-sulfonic acid, used in dilute concentrations are preferredfor effecting the hydrolysis; Temperatures ranging from about 0 to C.are usually employed to accomplish the hydrolysis. At room temperature,several minutes to three hours are ordinarily adequate to complete thereaction. The heavy precipitate of product is filtered from the reactionmixture and washed with an organic solvent and dried under vacuum.

The epoxy formate is also converted to S-pregnene- 3,17a-diol-20-one byreacting with a basic substance. Water must be present unless reactionis run in alcohol. The reactants are preferably brought together in asolvent. Suitable solvents are methanol, ethanol, hexane, benzene,toluene, xylene, petroleum ether, ether, dioxane, tetrahydrofuran andthe like. The basic substance may be any of .the conventional bases,such as an alkali metal or alkali metal hydroxide, carbonates,bicarbonate or the like, butis it preferred to use an hydroxide as forexample, sodium hydroxide, potassium methoxide, or potassium hydroxide.The reaction may be carried out at from 0 to 70 C. At room temperaturethe reaction requires from 30 to minutes for completion. On completionof the reaction the reaction mixture is neutralized by addition of anacid as for example, glacial acetic acid, and then the solution ispartially concentrated by evaporation under vacuum. The product isprecipitated from the reaction mixture by addition of water and is thenfiltered and washed with water.

The 5-halo-pregnene-3,17a-diol-20-one is oxidized to The oxidation ispreferably carried out with a chromic anhydridepyridine complex,although other selective oxidizing agents may be used, such as chromicacid. The oxidation may be carried out at a wide range of temperatures,although preferably below 50 C. Within the preferred temperature range,with the preferred oxidation agent, the reaction requires from 6 to 24hours. The product can be separated from the reaction mixture byconventional means.

a basic substance to form .4-pregnan-l7a-ol-3,20-dione.

This reactionis: generally carried: out; under anhydrous conditions. Thereactants are preferably-brought=together in a solvent. Suitablesolvents are methanol, ethanol, hexane, benzene, toluene, xylene,petroleum ether,'ether dioxane, tetrahydrofuran and the like. The basicsubstance may be any of the conventional bases, such as an alkali: oralkaline earth metal-hydroxide,carbonate, bicarbonate or the like but itis preferredtouse a hydroxide as for example, sodium hydroxide or,potassium hydroxide. The reaction may be carried out at from to 17 C. Atroom temperature the reaction requiresfrom 30 to 120 minutes forcompletion. On completion of the reaction the reaction mixture isneutralizedby addition of an acid as for example, glacial aceticacid,and then the solution is partially concentrated by evaporation undervacuum. The product is precipitated from the reaction mixture byaddition of water and is then filtered and washed with water.

The following examples are given forp'urposes of illustration:

Example 1 38-ACETOXY-5n-CHLORO-2 O-B ROMO-BISNORCHOLANAL A solution'of14.5 grams (0.03 54 mole) of 3,8-acetoxy- Sa-chlorobisnorcho-lanal in.200' ml. of chloroform was treated with ten grams (0.1 mole) ofanhydrous calcium carbonate and stirred at 28 C. To this slurry 46milliliters of cholorform solution containing 5.5 grams (0.0344 mole) ofbromine was added dropwise over a period of one-half hour and thereaction mixture stirred for two hours. After filtering to removecalcium carbonate the chloroform solution was washed with dilute sodiumiodide, sodium thiosulfate solution and then with dilute sodiumbicarbonate solution and finally dried over anhydrous sodium carbonate.The chloroform layer was then evaporated almost to dryness under vacuumand 100 milliliters of 95% ethanol was added. Upon further concentrationthe main portion of product precipitated. After standing overnight inthe refrigerator the product, 3,8-acetoxy-5ot chloro 2Obromobisnorcholanaldehyde, was filtered, washed with 50 milliliters of95% ethanol and dried under vacuum; yield 10.6 grams, melting point175179 C., [a] +13.4 (chloroform). Analysis. Calcd. for C24H3603C1B1'2C, 59.07; H, 7.44. Found: C, 58.79; H, 7.43.

Example 2 3/3-ACETOXY-5a-CHLORO-17 (2O -BISNO"RCHOLENAL Thirty-threegrams (0.068 mole) of 35-acetoxy-5w chloro-20-bromobisnorcholanal in1320 milliliters of dimethylformamide containing 5.5 grams (0.068 mole)of hydrogen bromide was allowed to stand at 28 C. for four days. Thesolution was then stirred and cooled in an ice bath while 600milliliters of water was added. After stirring for three hours theproduct was filtered, washed with water and dried under vacuum to yield26.8 grams of essentially pure 35-acetoxy-5u-chloro47(20)-bisnorcholenal, melting point l94-195 C., x maximum 2540, E percent 376.Recrystallization from methanol gave an analytical sample with the sameultraviolet absorption. Analysis.Calcd. for C24H3503Cl: C, 70.82; H,8.67; Cl, 8.71. Found: C, 70.51; H, 8.51; CI, 8.5 8.

Example 3 3B-ACETOXY-5a-CHLORO-17 (20)-BISNOTCHOLENAL Two grams (5millimoles) of 3B-acetoxy-5a-chloro bisnorcholanaldehyde and 0.04 gramof p-toluene sulfonic acid were dissolved in 80 milliliters ofdimethylformamide and stirred at 28 C. while 0.8 gram (5 millimoles) ofbromine in 7 milliliters of dimethylformamide was added dropwise overthe course of three hours. After standing at normal room temperature for24 hours the reaction mixture was cooled in an ice bath and diluted with80 milliliters of water. The resulting slurry was stirred for an hourand then filtered. The product was washed well 7 Boiling with ethylacetate dissolved little gamma Example 4 3,3-ACETOXY 5a-CHLOR0-1720-EPOXYPREGNAN -20-OL FORMATE I A solution containing 15.7 grams(0.0386fmole) of 3,3 'ac'etoxy 5a 4 chlo'ro 17(20) bisnorcholenaldehydein 150 milliliters of dry benzene at 10 C. was treated with 56 grams(0.309 mole) of perphthalic acid in 435 milliliters of ethyl acetate.The reaction mixture,

after standing two days at normal room temperature,

was filtered torem'ove insoluble phthalic acid and washed four timeswith 50'0milliliters of 10% sodium carbonate solution. carbonate andevaporated to dryness under vacuum to yield 15.1 grams; melting point'139-142" C.; [a] -5.2' (chloroform). The infrared spectrum of the crudereaction product was compatible with the epoxy formate formulation andelemental analysis agreed with calculated values. Analysis.Calcd. forC24H'3505C1: C, 65.66; H, 8.04; CI, 8.08. Found: C, 65.64; H, 7.97; Cl,8.12. i

' Example 5 5-PREGNENE-3B,17a-DIOL-20-OCNE One gram (2.4 millimoles) of3fl-acetoxy-5a-chloro- 17,20-epoxypre'gnan-2 0-ol formate was dissolvedin 150 milliliters of ethanol at 30 C. and treated with 30 millilitersof 215 M sodium hydroxide solution. After standing for ninety minutes atnormal room temperature 6 milliliters of glacial acetic acid was addedand the solution was partially evaporated under vacuum. The product wasprecipitated by dilution with 75 milliliters of water and refrigeratedovernight The reaction mixture was filtered; the solid was washed withwater and dried under vacuum to yield- 0.55 gram of product,5-pregnene-3p,17ot-diol-20-one, melting at 2002l5 C. Recrystallizationfrom ethanol gave product melting at 205-210 C. which was not depressedupon mixture with authentic 5-pregene-3p,l7a-diol-20-one.Analysis.-Calcd. for C21H32O3. C, 75.85; H, 9.70. Found: C, 75.41; H,9.66. 1

Example 6 5a-CHLORO-PREGNANE-3B,17a-DIOL-20-ONE A slurry of 2.5Sa-chloro 17,20 epoxypregnan 20-01 formate in ml. of methanol wastreated at normal room temperature with 12.5 milliliters of concentratedhydrochloric acid. A greenish-blue color developed and within an hoursolution was practically complete. The. reaction mixture Was allowed tostand overnight and then was cooled for one hour in the refrigerator.The heavy precipitate of product, 5a-chloropregnane 3[3,17oc diol-20-one, Was filtered, washed with methanol and dried under vacuum; weight1.0 gram, melting point 200-205 C. of the product but raised the meltingpoint to 205 210 C. The infrared sprectrum showed hydroxyl at 2.82 ,aand 2.98 pa, carbonyl at 5.90 a and no acetate grouping. Rotation inpyridine solution [a] 25+1 C. Analysis.-Calcd. for C21HaaO3Cl: C, 68.36;H, 9.02; Cl, 9.61. Found: C, 68.33; H, 9.03; Cl, 9.51.

Example 7 e-mmoNmN-l7a-0L-3,20-DIONE A chromic anhydride-pyridinecomplex was formed by The organic layer was dried over sodium' grams(5.7 millimoles) of Bfi-acetoxy- 7 1 adding 1.3' grams (13 millirnoles)of ehromic-anhydride in small portions with stirring to 13 millilitersofpyridine while keeping the temperature below 25 C. To this stirredslurry was added 1.3 grams (3.5 millimoles) of a-Cl1lOIO-1Jfgfl3fl6 3/317; diol 20 one in 26 milliliters of pyridine. No heat of reaction wasobserved but within one-half hour the mixture had become dark brown.After stirring overnight the reaction was poured into 500 milliliters ofdilute sodium hydroxide solution. The precipitated product,Sa-chIoro-pregnan 17m ol- 3,20-dione was stirred for one hour, filteredand washed with water.

The product was dissolved in milliliters of pyridine and 50 millilitersof methanol, filtered to remove insoluble inorganic material and treatedwith 19 milliliters of 2.5 molar sodium hydroxide solution at roomtemperature for one hour. The reaction mixture was then diluted with 100milliliters of water and refrigerated for one hour. Filtration of thesolid precipitate, followed by washing with water and drying undervacuum yielded 0.6 gram of 17e-hydroxyprogesterone, melting point200-212 C., 7\ maximum 2420 A., E percent 488. A sample for analysis wasrecrystallized from ethanol, melting point 2l3-2l8 C. Identity of thesample with 2111-. thentic material was established by infrared analysisand mixed melting point. Analysis.Ca1cd. for C21Hao03: C, 76.32; H,9.15. Found: C, 76.77; H, 9.58.

Any departure from the above description which conforms to the presentinvention is intended to be included in the scope of the claims.

What is claimed is:

1. Compounds having the structural formula:

CHSO

wherein R is a hydrocarbon radical containing less than 9 carbon atomsand X is a halogen.

2. A process which comprises reacting V 3-(0i;R)-5helo-17(20)-bisn0reholenal wherein R -is a hydrocarbon groupcontaining less than 9 carbon atoms, with an organic peracid to form thecorresponding References Cited in the file of this patent UNITED STATESPATENTS 2,573,417 Ehrenstein Oct. 30, 1951 2,656,349 Ruzicka Oct. 20,1953 2,671,084 Lincoln Mar. 2, 1954 2,704,768 Colton Mar. 22, 1955

1. COMPOUNDS HAVING THE STRUCTURAL FORMULA: